Orthopedic fastener device

ABSTRACT

Orthopedic fastener devices for fixation of fractured bones are disclosed. The orthopedic fastener device is in the form of an orthopedic fastener having an IM nail coated on its external surface with a bioabsorbable or biodegradable hydrogel. Also disclosed are hydrogel coated orthopedic fastener devices in the form of a K-wire or bone screw, a method for stabilizing a fractured long bone fracture by inserting an orthopedic fastener into the medullary canal of the bone and a kit for fastener implantation.

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 12/539,314, filed Aug. 11, 2009, which is acontinuation-in-part application of U.S. patent application Ser. No.12/417,122, filed Apr. 2, 2009, now U.S. Pat. No. 8,246,691, whichclaims priority to U.S. Patent Application Ser. No. 61/129,203, filedJun. 11, 2008. The entirety of all of the aforementioned applications isincorporated herein by reference.

FIELD

The present invention generally relates to medical devices and, inparticular, to orthopedic fastener devices for the fixation of bonefragments.

BACKGROUND

There are about 500,000 fractures of the tibia and fibula, 200,000metacarpal fractures and over 400,000 distal radial fractures in theUnited States each year. In many cases the bones are immobilized byplacing a cast on the fractured limb. However, casts often mustimmobilize a substantial length of the limb, can be heavy, inconvenientand limit the use of the limb, including significantly limiting themobility of the subject. Additionally, there is a risk of non-union ofthe fractured ends, resulting in a failure of the fractured ends tounite. Non-unions may require additional operations to promote fracturehealing. In addition to the risk of general anesthesia and earlypost-operative venous thromboembolism complications in patients whorequire re-operation face additional rehabilitation and time off fromwork.

Another means for fixation of long bone fragments includes the use ofKirschner wires (K-wires) drilled into the bone fragments and held inplace by an external fixation device. However, external fixation devicesmay not be practical in all situations, as they may interfere with somefunctions. Additionally, because K-Wires pass through the skin, extendedpresence of conventional K-Wires may form a potential passage forbacteria and cause infection. Additionally, conventional K-Wires canmigrate, causing a loss of fixation of the bone fragments.

Still another means for fixation of long bone fragments includes theinsertion of an intramedullary (IM) nail into the lumen, or medullarycavity, of the long bone. The IM nail spans the fracture and is securedto the bone on either side by screws through the bone. IM nails aretypically manufactured from a durable metal material and may be left inthe bone after healing. In some instances, however, surgical removal ofa durable IM nail is required, again exposing a subject to the risks ofgeneral anesthesia, venous thromboembolism, rehabilitation and time offfrom work. Additionally, present IM nails do not fill up the entirewidth of the lumen in the bone, potentially allowing the fracture tounite in a displaced, off-set or crooked manner, resulting in improperhealing of the fracture. Accordingly, there exists a need for animproved IM nail in the form of an orthopedic fastener that isbiodegradable and fills the lumen to prevent off-set healing of thefracture.

SUMMARY

One aspect of the present application relates to an orthopedic fastenerfor internal fixation of a fractured long bone, comprising an IM nailcoated on its external surface with a bioabsorbable or biodegradablehydrogel.

Another aspect of the present application relates to a method forstabilizing a bone fracture. The method includes inserting an orthopedicfastener comprising an IM nail coated on its external surface with abioabsorbable or biodegradable hydrogel into the canal of a bone havinga fracture.

Still another aspect of the present application relates to a kit fororthopedic fastener implantation in a fractured long bone. The kitincludes: an orthopedic fastener comprising an IM nail coated on itsexternal surface with a bioabsorbable or biodegradable hydrogel; a guidewire or rod; and a pusher tube that is movable along or over the guidewire or rod.

Still another aspect of the present application relates to an orthopedicfastener device for fixation of a fractured bone comprising a K-Wirecoated on its external surface with a bioabsorbable or biodegradablehydrogel.

Still another aspect of the present application relates to an orthopedicfastener device for fixation of a fractured bone comprising a bone screwcoated on its external surface with a bioabsorbable or biodegradablehydrogel.

BRIEF DESCRIPTION OF DRAWINGS

The present invention can be better understood by reference to thefollowing drawings, wherein like references numerals represent likeelements. The drawings are merely exemplary to illustrate certainfeatures that may be used singularly or in combination with otherfeatures and the present invention should not be limited to theembodiments shown.

FIG. 1 shows an exemplary illustration of a displaced metacarpalfracture.

FIG. 2 shows an X-Ray image of an example of a displaced ulnar fracture.

FIG. 3 shows an X-Ray image of an example of a displaced tibia fracture.

FIG. 4 is an isometric view of an exemplary orthopedic fastener.

FIGS. 5A and 5B show an exemplary orthopedic fastener. FIG. 5A is a sideplane view. FIG. 5B is a side cross sectional view.

FIGS. 6A and 6B show an exemplary orthopedic fastener as applied to adisplaced long bone fracture. FIG. 6A is a side plane cross sectionalview. FIG. 6B is a cross sectional view from an end of the bone.

FIGS. 7A and 7B show an exemplary orthopedic fastener in final state asapplied to a displaced long bone fracture. FIG. 7A is a side plane crosssectional view. FIG. 7B is a cross sectional view from an end of thebone.

FIG. 8 is an isometric view of an exemplary K-wire.

FIG. 9 is an isometric view of an exemplary bone screw.

DETAILED DESCRIPTION

The practice of the present invention will employ, unless otherwiseindicated, conventional medical devices and methods within the skill ofthe art. Such techniques are explained fully in the literature. Allpublications, patents and patent applications cited herein, whethersupra or infra, are hereby incorporated by reference in their entirety.

The present application relates to an orthopedic fastener device for thefixation of bone fragments or bone fractures. The orthopedic fastenerdevice contains an elongated metal or alloy body coated with a hydrogel.In certain embodiments, the orthopedic fastener device is an orthopedicfastener coated with a hydrogel. In other embodiments, the orthopedicfastener device is a K-wire coated with a hydrogel. In yet otherembodiments, the orthopedic fastener device is a bone screw coated witha hydrogel.

As used herein, the term “fastener” refers to something that attaches orjoins two parts together. In some embodiments, a fastener is a hardwaredevice that mechanically joins or affixes two or more objects together.As used herein, the term “orthopedic fastener” refers to a fastenerdevice which is implanted within the hollow center of a fractured boneto stabilize and/or reinforce the fractured bone.

As used herein, the term “long bone” refers to any bone having a shaftand two extremities. Long bones are found in the limbs and include theclavicle, humerus, radius, ulna, femur, tibia, fibula, metacarpal andmetatarsal bones.

One aspect of the present application relates to an orthopedic fastenerfor internal fixation of a fractured long bone comprising an IM nailcoated on its external surface with a bioabsorbable or biodegradablehydrogel.

In some embodiments, the IM nail comprises a center lumen to accommodatea guide wire.

In particular embodiments, the orthopedic fastener degrades in situ byhydrolytic reactions, enzymatic reactions, alkaline or pH changes.

In some embodiments, the IM nail is manufactured from a biodegradablemetal or biodegradable alloy. In further embodiments, the biodegradablemetal is magnesium. In other further embodiments, the biodegradablealloy comprises magnesium. In still other, or related, furtherembodiments, the biodegradable alloy comprises rare earth materials. Inyet still other, or related, further embodiments, the biodegradablealloy comprises a magnesium alloy and chitin. In yet still otherembodiments, the biodegradable alloy comprises a magnesium and chitinalloy.

In some embodiments, the IM nail is made of a chitin and chitosan,N-acylchitosan hydrogel and magnesium alloy with rare earth elements.

In particular embodiments, the hydrogel is a chitin chitosan,N-acylchitosan hydrogel.

In some embodiments, the hydrogel swells to about 30% of its maximaldiameter within 10 minutes after coming in contact with moisture.

Another aspect of the present application relates to a method forstabilizing a bone fracture comprising, inserting an orthopedic fastenerinto the medullary canal of a bone having a fracture, wherein saidorthopedic fastener comprises an IM nail coated on its external surfacewith a bioabsorbable or biodegradable hydrogel.

In some embodiments, the orthopedic fastener is placed through the bonecortex.

In particular embodiments, the orthopedic fastener degrades in situ byhydrolytic reactions, enzymatic reactions, alkaline or pH changes.

Yet another aspect of the present application relates to a kit forfastener implantation in a fractured long bone, said kit comprising: anorthopedic fastener comprising an IM nail coated on its external surfacewith a bioabsorbable or biodegradable hydrogel; a guide wire or rod; anda pusher that is movable along or over the guide wire or rod.

In some embodiments, the IM nail is made of a bioabsorbable material.

In particular embodiments, the IM nail further comprises a center lumento accommodate the guide wire.

In some embodiments, the IM nail is made of a magnesium alloy andchitin.

In some embodiments, the IM nail is made of a magnesium and chitinalloy.

In other embodiments, the IM nail is made with a magnesium core coatedwith a chitin chitosan, N-acylchitosan hydrogel outer layer.

In still other embodiments, the IM nail is made of a chitin andchitosan, N-acylchitosan hydrogel and magnesium alloy with raw earthelements.

Still another aspect of the present application relates to an orthopedicfastener device for fixation of a fractured bone comprising a K-Wirecoated on its external surface with a bioabsorbable or biodegradablehydrogel.

Yet still another aspect of the present application relates to anorthopedic fastener device for fixation of a fractured bone, comprisinga bone screw coated on its external surface with a bioabsorbable orbiodegradable hydrogel.

In some embodiments, the bone screw is a Scaphoid screw for fixation ofa fractured carpal or tarsal bone.

For reference, FIG. 1 shows an illustration of a hand having displacedfractures of the first and fifth metacarpal bones.

FIG. 2 is an exemplary X-ray image of a forearm having a displacedfracture of the radius.

FIG. 3 is an exemplary X-ray image of a lower leg having a displacedfracture of the tibia.

IM Nail

One aspect of the present application relates to an orthopedic fastenerfor internal fixation of a fractured long bone, comprising an IM nailcoated on its external surface with a bioabsorbable or biodegradablehydrogel. The hydrogel swells after implant of the orthopedic fastener,creating an internal soft fixation of the fracture, assisting with therealignment of displaced fractures. The hydrogel degrades over timebased upon enzymatic or pH interaction with the subject's internalmilieu. Accordingly, no subsequent or repeat surgical procedures arerequired to remove the hydrogel.

As used herein, the term “intramedullary nail (IM nail),” also known as“intramedullary rod,” “inter-locking nail” or “Kiintscher nail,” is ametal rod or tube forced into the medullary cavity of a bone. IM nailshave long been used to treat fractures of long bones of the body. The IMnail can be manufactured from durable metal materials or frombiodegradable metals or metal alloys as used in other biodegradablefasteners described herein.

FIG. 4 is an isometric view of an exemplary orthopedic fastener 10 forinternal fixation of a fractured long bone. The orthopedic fastenercomprises an IM nail 20 coated on its external surface with abioabsorbable or biodegradable hydrogel 15.

FIG. 5A is a side plane view of the exemplary orthopedic fastener ofFIG. 4, while FIG. 5B is a side cross sectional view of the exemplaryorthopedic fastener as viewed in the direction of the arrows whenbisected at line 2-2. The orthopedic fastener comprises an IM nail 20coated on its external surface 20 a with a bioabsorbable orbiodegradable hydrogel 15

The hydrogel 15 swells after implant of the orthopedic fastener 10,creating an internal soft fixation of the fracture, assisting with therealignment of displaced fracture as illustrated in FIGS. 6A and 6B.

In FIG. 6A the displaced fracture 30 a of the long bone 30 isillustrated in a side plane cross sectional view, with orthopedicfastener 10 positioned in the medullary cavity 30 b. FIG. 6B furtherillustrates, in a cross-sectional view from an end of the bone, theorthopedic fastener 10 placement in the medullary cavity 30 b prior toexpansion of the hydrogel 15.

In FIG. 7A, the orthopedic fastener 10 is illustrated in a side planecross sectional view with the expansion of the hydrogel 15, comprisingthe realignment of the displaced fracture 30 a of the fractured longbone 30. The cross-sectional view from an end of the bone in FIG. 7Bfurther illustrates the orthopedic fastener 10 with expanded hydrogel 15in the medullary cavity 30 b. The hydrogel 15 degrades over time basedupon enzymatic or pH interaction with the subject's internal milieu.Accordingly, no subsequent or repeat surgical procedures are required toremove the hydrogel.

The fastener body may further include a center lumen to accommodate aguide wire. This center lumen may provide additionally flow throughputafter the removal of guide wire.

In a particular embodiment, the orthopedic fastener is imbedded withbarium sulphate or other metallic particles or contrast agents toenhance imaging.

In some embodiments, the orthopedic fastener is coated with abiodegradable material to control its properties, including mechanicalstrength, biocompatibility, biodegradation, diffusibility, andabsorption properties.

In particular embodiments, the IM nail is tubular. In a relatedembodiment, the IM nail further contains a center lumen. In otherparticular embodiments, the IM nail is V-shaped.

In some embodiments, the orthopedic fastener degrades in situ byhydrolytic reactions, enzymatic reactions, alkaline or pH changes.

In some embodiments, the IM nail is manufactured from a durable metal.In a further embodiment, the durable metal is titanium. In anotherfurther embodiment, the durable metal is an alloy comprising titanium.In a still further embodiment, the alloy comprises titanium and nickel.In a yet still further embodiment, the alloy comprising titanium andnickel is nitinol.

In some embodiments, the IM nail is manufactured from a biodegradablemetal or biodegradable alloy. In a further embodiment, the biodegradablemetal is magnesium. In another further embodiment, the biodegradablealloy comprises magnesium. In a still further embodiment, the magnesiumalloy additionally includes rare earth materials. In another or relatedstill further embodiment, the biodegradable alloy comprises a magnesiumand chitin alloy. In another or related still further embodiment, thebiodegradable alloy comprises a magnesium alloy and chitin. In a yetfurther embodiment, the IM nail is made of a chitin and chitosan,N-acylchitosan hydrogel and magnesium alloy with rare earth elements.

In some embodiments, the hydrogel is a chitin chitosan, N-acylchitosanhydrogel. In particular embodiments, the hydrogel may absorb moistureand expand in situ at the treatment site. For example, the hydrogelwould swell once it comes into contact with various body fluids. As usedherein, the “pre-implantation diameter Dpre” refers to the largestdiameter of an orthopedic fastener body before implantation and the“post-implantation diameter Dpost” refers to the largest diameter of theorthopedic fastener body after implantation.

In some embodiments, the hydrogel swells to about 10-90%, 10-70% or10-50% of its maximal diameter within 10, 20 or 30 minutes after comingin contact with moisture. In some embodiments, the hydrogel swells toabout 10% of its maximal diameter within 10, 20 or 30 minutes aftercoming in contact with moisture. In some embodiments, the hydrogelswells to about 20% of its maximal diameter within 10, 20 or 30 minutesafter coming in contact with moisture. In some embodiments, the hydrogelswells to about 30% of its maximal diameter within 10, 20 or 30 minutesafter coming in contact with moisture. In some embodiments, the hydrogelswells to about 40% of its maximal diameter within 10, 20 or 30 minutesafter coming in contact with moisture. In some embodiments, the hydrogelswells to about 50% of its maximal diameter within 10, 20 or 30 minutesafter coming in contact with moisture. The hydrogel swells or expands byabsorbing of fluids and improves the connection and support of the innerwall of the bone canal.

In another embodiment, the orthopedic fastener is imbedded or coatedwith barium sulphate or other contrast agents to enhance imaging of thefastener.

In another embodiment, the orthopedic fastener is additionally coatedwith a biodegradable material to control its properties, includingmechanical strength, biocompatibility, biodegradation, diffusibility,and absorption properties.

In another embodiment, the orthopedic fastener degrades in situ byhydrolytic reactions, enzymatic reactions, alkaline or pH changes.

The shape, length and diameter of the orthopedic fastener areapplication dependent. The elongated fastener body can be straight orcurved or in the shape to match the curvature of a particular bone. Eachtype of orthopedic fastener is designed to fit within a specific bone.Therefore, the shape, length, and diameter of fasteners differ by typeto accommodate and support different sized lumens and different clinicalneeds. For example, each major orthopedic fastener application, such asclavicle, humerus, radius, ulna, femur, tibia, fibula, metacarpal ormetatarsal, requires a different diameter and shape to enable placement,to remain in place after placement, to stabilize and support the bone itis placed in, and to allow conformance to the normal anatomy.

As used herein, the diameter of a fastener refers to the width acrossthe shaft of the fastener body, which is also referred to as the “majordiameter.” In one embodiment, the fastener has a uniform diameter. Inanother embodiment, the fastener has a variable diameter. In oneembodiment, the diameter at the distal end is smaller than the diameterat the proximal end. In another embodiment, the diameter at the proximalend is smaller than the diameter at the distal end. In yet anotherembodiment, the diameters at the distal end and the proximal end areboth smaller than the diameter at the middle section of the fastener. Incases where a fastener has a variable diameter, the “major diameter” isthe largest diameter along the fastener body.

As used herein, the term “maximal diameter” of a hydrogel coatedfastener refers to the maximum width across the shaft of the fastenerbody after the hydrogel coating of the fastener is fully hydrated.

In one embodiment, the fastener is delivered to the treatment site in amedullary canal with a pusher rod that pushes the fastener through ahole drilled in one end of the bone. The pusher rod travels over a guidewire. The pusher rod is designed in such a way to attach to the ends ofthe fastener to assist with directing the delivery. In one embodiment,the pusher rod interlocks with the proximal end of the fastener in amale/female fashion, much the same way a wrench fits over a nut.

In some embodiments, the IM nail may also be made with a bioabsorbablenon-metal material. Examples of bioabsorbable non-metal materialsinclude, but are not limited to, polylactic acid or polylactide (PLA),polyglycolic acid or polyglycolide (PGA), poly-ε-caprolactone (PCL),polyhydroxybutyrate (PHB), and co-polymers thereof.

In one embodiment, the bioabsorbable material of the fastener and/orhydrogel is degraded based on varying levels of pH. For example, thematerial may be stable at a neutral pH but degrades at a high pH.Examples of such materials include, but are not limited to chitin andchitosan. In another embodiment, the bioabsorbable material isdegradable by enzymes, such as lysozymes.

In another embodiment, the bioabsorbable material is embedded with, orconfigured to carry, various agents or cells. The agents may be coupledto the outer and/or inner surfaces of the orthopedic fastener body orintegrated into the bioabsorbable material of the hydrogel. In oneembodiment, the fastener has a hollow center lumen so that agents may beplaced inside the lumen to increase the dose release. The fastener canadditionally have multiple reservoirs, one inside the other, so thatwhen the outer layer is absorbed the next reservoir is exposed and afurther release of a larger dose of the chosen agents or cells. Thechosen agent or cells may also be mixed with the polymer for sustainedrelease.

Examples of agents that can be embedded into or carried by a fastenerinclude, but are not limited to, small molecule drugs, biologicals andgene transfer vectors.

Examples of biologicals include, but are not limited to, antimicrobialagents, chemotherapeutic agents, hormonal agents and anti-hormonalagents. The term “antimicrobial agent” as used in the present inventionmeans antibiotics, antiseptics, disinfectants and other syntheticmoieties, and combinations thereof Exemplary chemotherapeutic agentsinclude but are not limited to cis-platinum, paclitaxol,5-flourouracial, gemcytobine and navelbine. The chemotherapeutic agentsare generally grouped as DNA-interactive agents, antimetabolites,tubulin-interactive agents, hormonal agents, hormone-related agents, andothers such as asparaginase or hydroxyurea. Hormonal agents include:estrogens, conjugated estrogens and ethinyl estradiol anddiethylstilbestrol, chlorotrianisene and idenestrol; progestins such ashydroxyprogesterone caproate, medroxyprogesterone, and megestrol;androgens such as testosterone, testosterone propionate;fluoxymesterone, methyltestosterone; adrenal corticosteroids are derivedfrom natural adrenal cortisol or hydrocortisone. They are used becauseof their anti-inflammatory benefits as well as the ability of some toinhibit mitotic divisions and to halt DNA synthesis. These compoundsinclude prednisone, dexamethasone, methylprednisolone, and prednisolone.Antihormonal agents include antiestrogenic agents such as tamosifen,antiandrogen agents such as Flutamide; and antiadrenal agents such asmitotane and amminoglutethimide.

Gene transfer vectors are capable of introducing a polynucleotide into acell. The polynucleotide may contain the coding sequence of a protein ora peptide, or a nucleotide sequence that encodes an iRNA or antisenseRNA. Examples of gene transfer vectors include, but are not limited to,non-viral vectors and viral vectors.

One aspect of the present application relates to an orthopedic fastenerfor internal fixation of a fractured long bone comprising an IM nailcoated on its external surface with a bioabsorbable or biodegradablehydrogel.

In a particular embodiment, the IM nail comprises a center lumen toaccommodate a guide wire.

In another particular embodiment, the orthopedic fastener degrades insitu by hydrolytic reactions, enzymatic reactions, alkaline or pHchanges.

In another particular embodiment, the IM nail is manufactured from abiodegradable metal or biodegradable alloy. In a related embodiment, thebiodegradable metal is magnesium. In another related embodiment, thebiodegradable alloy comprises magnesium. In another related embodiment,the biodegradable alloy comprises rare earth materials. In anotherrelated embodiment, the biodegradable alloy comprises a magnesium andchitin alloy. In a further related embodiment, the IM nail is made of achitin and chitosan, N-acylchitosan hydrogel and magnesium alloy withrare earth elements.

In another particular embodiment, the hydrogel is a chitin chitosan,N-acylchitosan hydrogel.

In another particular embodiment, the hydrogel swells to about 30% ofits maximal diameter within 10 minutes after coming in contact withmoisture.

Another aspect of the present application relates to a method forstabilizing a bone fracture comprising, inserting an orthopedic fastenerinto the medullary canal of a bone having a fracture, wherein saidorthopedic fastener comprises an IM nail coated on its external surfacewith a bioabsorbable or biodegradable hydrogel.

In a particular embodiment of the method, the orthopedic fastener isplaced through the bone cortex.

In another particular embodiment of the method, the orthopedic fastenerdegrades in situ by hydrolytic reactions, enzymatic reactions, alkalineor pH changes.

Another aspect of the present application relates to a kit for fastenerimplantation, said kit comprising: an orthopedic fastener for internalfixation of a fractured long bone, comprising an IM nail coated on itsexternal surface with a bioabsorbable or biodegradable hydrogel; a guidewire; and a pusher that is movable along the guide wire.

In a particular embodiment of the kit, the IM nail is made of abioabsorbable material.

Still another aspect of the present application relates to a kit forfastener implantation in a fractured long bone. The kit includes: anorthopedic fastener comprising an IM nail coated on its external surfacewith a bioabsorbable or biodegradable hydrogel; a guide wire; and apusher tube that is movable along the guide wire.

In another particular embodiment of the kit, the IM nail is made with amagnesium core coated with a chitin chitosan, N-acylchitosan hydrogelouter layer.

In another particular embodiment of the kit, the IM nail is made of achitin and chitosan, N-acylchitosan hydrogel and magnesium alloy withraw earth elements.

K-Wire

Another aspect of the present application relates to a Kirschner wire(K-Wire) coated with a hydrogel (coated K-Wire) as described herein foran IM Nail coated with hydrogel. K-wires are sterilized, sharpened,smooth metal or alloy pins that are used to hold bone fragments together(pin fixation) or to provide an anchor for skeletal traction. The pinsare often driven into the bone through the skin (percutaneous pinfixation) using a power or hand drill. Following placement of the coatedK-Wire, the hydrogel swells, fixing the K-Wire in place in the bonefragments. The swelling of the hydrogel improves the alignment of thefragments and reduces or prevents the migration of the K-Wire. Anexemplary K-Wire 40 is shown in FIG. 8.

In particular embodiments, the coated K-Wire comprises a smooth K-Wire.In other embodiments, the coated K-Wire comprises a threaded K-Wire. Instill other embodiments, the coated K-Wire comprises a Denham pin.

In some embodiments, the K-Wire is made of a durable metal. Inparticular further embodiments, the durable metal is stainless steel. Inanother embodiment, the durable metal is titanium. In a furtherembodiment, the durable metal is an alloy comprising titanium. In astill further embodiment, the alloy comprises titanium and nickel. In ayet still further embodiment, the alloy comprising titanium and nickelis nitinol.

In some embodiments, the K-Wire is manufactured from a biodegradablemetal or biodegradable alloy. In a further embodiment, the biodegradablemetal is magnesium. In another further embodiment, the biodegradablealloy comprises magnesium. In a still further embodiment, the magnesiumalloy additionally includes rare earth materials. In another or relatedstill further embodiment, the biodegradable alloy comprises a magnesiumalloy and chitin. In another or related still further embodiment, thebiodegradable alloy comprises a magnesium and chitin alloy. In a yetfurther embodiment, the K-Wire is made of a chitin and chitosan,N-acylchitosan hydrogel and magnesium alloy with rare earth elements.

In some embodiments, the hydrogel coating of the K-Wire is a chitinchitosan, N-acylchitosan hydrogel. In particular embodiments, thehydrogel may absorb moisture and expand in situ at the treatment site.For example, the hydrogel would swell once it comes into contact withvarious body fluids. As used herein, the “pre-implantation diameterDpre” refers to the largest diameter of a coated K-Wire beforeimplantation and the “post-implantation diameter Dpost” refers to thelargest diameter of the coated K-Wire after implantation.

In some embodiments, the hydrogel coating of the K-Wire swells to about10-90% of its maximal diameter within 10, 20 or 30minutes after comingin contact with moisture. In some embodiments, the hydrogel swells toabout 10% of its maximal diameter within 10, 20 or 30 minutes aftercoming in contact with moisture. In some embodiments, the hydrogelswells to about 20% of its maximal diameter within 10, 20 or 30 minutesafter coming in contact with moisture. In some embodiments, the hydrogelswells to about 30% of its maximal diameter within 10, 20 or 30 minutesafter coming in contact with moisture. In some embodiments, the hydrogelswells to about 40% of its maximal diameter within 10, 20 or 30 minutesafter coming in contact with moisture. In some embodiments, the hydrogelswells to about 50% of its maximal diameter within 10, 20 or 30 minutesafter coming in contact with moisture. The hydrogel swells or expands byabsorbing of fluids and improves the union and support of the bonefragments.

In particular embodiments, the coated K-Wire is attached to an externalfixation device.

In particular embodiments, the coated K-Wire is trimmed followingemplacement, such that the end of the coated K-Wire does not protrudefrom the bone or bone fragment.

Bone Screw

Another aspect of the present application relates to a bone screw coatedwith a hydrogel as described herein for an IM Nail coated with hydrogel.Bone screws, such as Scaphoid screws, are screws used to fix bonefractures. The bone screw has threads on both ends of the screw and isplaced completely inside the bone to hold the fractured pieces together.Following placement of the coated bone screw, the hydrogel swells,fixing the bone screw in place in the bone fragments. The swelling ofthe hydrogel improves the alignment of the fragments and reduces orprevents the migration of the bone screw. In one embodiment, the bonescrew is a Scaphoid screw for fixation of a fractured carpal bone ortarsal bone. Scaphoid fractures are the most common fracture of a carpalbone, representing about 2-7% of all fractures and over 70% of all handfractures presenting to emergency departments. An exemplary bone screw50 is shown in FIG. 9.

In some embodiments, the bone screw is made of a durable metal. Inparticular further embodiments, the durable metal is stainless steel. Inanother embodiment, the durable metal is titanium. In a furtherembodiment, the durable metal is an alloy comprising titanium. In astill further embodiment, the alloy comprises titanium and nickel. In ayet still further embodiment, the alloy comprising titanium and nickelis nitinol.

In another particular embodiment, the bone screw is manufactured from abiodegradable metal or biodegradable alloy. In a related embodiment, thebiodegradable metal is magnesium. In another related embodiment, thebiodegradable alloy comprises magnesium. In another related embodiment,the biodegradable alloy comprises rare earth materials. In anotherrelated embodiment, the biodegradable alloy comprises a magnesium alloyand chitin. In another related embodiment, the biodegradable alloycomprises a magnesium and chitin alloy. In a further related embodiment,the bone screw is made of a chitin and chitosan, N-acylchitosan hydrogeland magnesium alloy with rare earth elements.

In some embodiments, the hydrogel coating of the bone screw is a chitinchitosan, N-acylchitosan hydrogel. In particular embodiments, thehydrogel may absorb moisture and expand in situ at the treatment site.For example, the hydrogel would swell once it comes into contact withvarious body fluids. As used herein, the “pre-implantation diameterDpre” refers to the largest diameter of a coated bone screw beforeimplantation and the “post-implantation diameter Dpost” refers to thelargest diameter of the largest diameter of the coated bone screw iscapable to reach after implantation.

In some embodiments, the hydrogel coating of the bone screw swells toabout 10-90% of its maximal diameter within 10, 20 or 30 minutes aftercoming in contact with moisture. In some embodiments, the hydrogelswells to about 10% of its maximal diameter within 10, 20 or 30 minutesafter coming in contact with moisture. In some embodiments, the hydrogelswells to about 20% of its maximal diameter within 10, 20 or 30 minutesafter coming in contact with moisture. In some embodiments, the hydrogelswells to about 30% of its maximal diameter within 10, 20 or 30 minutesafter coming in contact with moisture. In some embodiments, the hydrogelswells to about 40% of its maximal diameter within 10, 20 or 30 minutesafter coming in contact with moisture. In some embodiments, the hydrogelswells to about 50% of its maximal diameter within 10, 20 or 30 minutesafter coming in contact with moisture. The hydrogel swells or expands byabsorbing of fluids and improves the connection and support of the innerwall of the bone canal.

The present invention is further illustrated by the following examplewhich should not be construed as limiting. The contents of allreferences, patents and published patent applications cited throughoutthis application, as well as the Figures and Tables, are incorporatedherein by reference.

EXAMPLE 1 Fixation of a Tibial Fracture

The subject is positioned on an operating or extension table in thesupine position. The knee of the injured leg is flexed at least throughninety degrees and a femoral holding device may be applied.

The entry point of the orthopedic fastener lies in the prolongation ofthe axis of the diaphysis at the upper margin of the tibia. Alongitudinal incision of about 25 mm is made at the lower margin of thepatella.

The tip of a guide rod is placed at the entry point and driven forwardthrough the bone into the medullary canal. A tissue protection sleeve isplaced over the guide rod and moved into contact with the externalsurface of the bone.

Inside the tissue protection sleeve, a cannulated awl is driven forwardover the guide wire with rotating movements in order to make the holelarge enough for the insertion of the orthopedic fastener.

The awl, tissue protection sleeve and guide rod are removed. A guidewire is inserted into the medullary canal, pushed forward into thedistal fragment and positioned centrally in the distal tibialmetaphysis.

The orthopedic fastener is inserted by hand over the guide wire into themedullary canal and a pusher, such as a slap hammer, is inserted ontothe guide wire. The orthopedic fastener is driven completely into themedullary canal using the pusher.

The guide wire is removed and the hydrogel is allowed sufficient time toexpand in the medullary canal and align the ends of the fragments.

The position of the orthopedic fastener in the tibia is fixed byapplying set screws through the bone into the distal and proximalregions of the IM nail.

Subsequently, following sufficient time for knitting of the bone at thefracture site, the set screws are removed and the orthopedic fastener isallowed to remain in the medullary canal for support of the bone untilthe orthopedic fastener is bioabsorbed by the subject's body.

The above description is for the purpose of teaching the person ofordinary skill in the art how to practice the present invention, and itis not intended to detail all those obvious modifications and variationsof it which will become apparent to the skilled worker upon reading thedescription. It is intended, however, that all such obviousmodifications and variations be included within the scope of the presentinvention, which is defined by the following claims. The claims areintended to cover the claimed components and steps in any sequence whichis effective to meet the objectives there intended, unless the contextspecifically indicates the contrary.

What is claimed is:
 1. An orthopedic fastener for internal fixation of afractured long bone comprising an IM nail coated on its external surfacewith a bioabsorbable or biodegradable hydrogel.
 2. The orthopedicfastener of claim 1, wherein the IM nail comprises a center lumen toaccommodate a guide wire.
 3. The orthopedic fastener of claim 1, whereinthe orthopedic fastener degrades in situ by hydrolytic reactions,enzymatic reactions, alkaline or pH changes.
 4. The orthopedic fastenerof claim 1, wherein the IM nail is manufactured from a biodegradablemetal or biodegradable alloy.
 5. The orthopedic fastener of claim 4,wherein the biodegradable metal is magnesium.
 6. The orthopedic fastenerof claim 4, wherein the biodegradable alloy comprises magnesium.
 7. Theorthopedic fastener of claim 4, wherein the biodegradable alloycomprises rare earth materials.
 8. The orthopedic fastener of claim 4,wherein the biodegradable alloy comprises a magnesium alloy and chitin.9. The orthopedic fastener of claim 1, wherein the IM nail is made of achitin and chitosan, N-acylchitosan hydrogel and magnesium alloy withrare earth elements.
 10. The orthopedic fastener of claim 1, wherein thehydrogel is a chitin chitosan, N-acylchitosan hydrogel.
 11. Theorthopedic fastener of claim 1, wherein the hydrogel swells to about 30%of its maximal diameter within 10 minutes after coming in contact withmoisture.
 12. A method for stabilizing a bone fracture comprising,inserting an orthopedic fastener into the medullary canal of a bonehaving a fracture, wherein said orthopedic fastener comprises an IM nailcoated on its external surface with a bioabsorbable or biodegradablehydrogel.
 13. The method of claim 12, wherein the orthopedic fastener isplaced through the bone cortex.
 14. The method of claim 12, wherein theorthopedic fastener degrades in situ by hydrolytic reactions, enzymaticreactions, alkaline or pH changes.
 15. A kit for fastener implantationin a fractured long bone, said kit comprising: an orthopedic fastenercomprising an IM nail coated on its external surface with abioabsorbable or biodegradable hydrogel; a guide wire; and a pusher thatis movable along the guide wire.
 16. The kit of claim 15, wherein the IMnail is made of a bioabsorbable material.
 17. The kit of claim 15,wherein the IM nail further comprises a center lumen to accommodate theguide wire.
 18. The kit of claim 15, wherein the IM nail is made of amagnesium alloy and chitin.
 19. The kit of claim 15, wherein the IM nailis made with a magnesium core coated with a chitin chitosan,N-acylchitosan hydrogel outer layer.
 20. The kit of claim 15, whereinthe IM nail is made of a chitin and chitosan, N-acylchitosan hydrogeland magnesium alloy with raw earth elements.
 21. An orthopedic fastenerdevice for fixation of a fractured bone comprising a K-Wire coated onits external surface with a bioabsorbable or biodegradable hydrogel. 22.An orthopedic fastener device for fixation of a fractured bone,comprising a bone screw coated on its external surface with abioabsorbable or biodegradable hydrogel.
 23. The orthopedic fastenerdevice of claim 22, wherein said bone screw is a Scaphoid screw forfixation of a fractured carpal or tarsal bone.